New research points to the possibility of even cleaner diesel engines in the future.
Not a pretty picture Image: US EPA |
The study, conducted by scientists at Sandia's Combustion Research Facility (CRF) in California, has been able to identify the sources of noxious carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions from engines using "Low-temperature combustion" (LTC).
By offering a better understanding of UHC and CO, the negative elements of an otherwise positive combustion process could be elimated, resulting in even cleaner diesel engines and further increased fuel efficiency.
LTC offers diesel engine designers a way of combatting the core, toxic pollutants created during conventional diesel combustion - NOx emissions and smoky particulate matter, or PM.
With catalytic converters not being an option for diesel engines, the only other solution to removing these has been the costly and less efficient alternative of complicated exhaust after-treatment systems.
The LTC strategy lowers the smog-producing NOx, produced by high-temperature combustion, by recirculating some of the diesel exhaust gases back into the engine, where they absorb the heat from combustion. The dilution effect reduces combustion temperatures and results in lower NOx formation.
The other pollutant, PM, is formed in regions where fuel concentrations are too high. To avoid this build-up, the LTC strategy allows fuel to be sprayed earlier in the engine cycle, giving the fuel more time to mix with air before combustion.
However, an unwanted by-product of LTC is increased UHC and CO which are both toxic and inefficient.